Allow URLs without protocol. (#238)

* Allow URLs without protocol.

gateways/cardconnect/cardconnect.go

@@ -6,6 +6,7 @@ import (
 	"io/ioutil"
 	"net/http"
 	"net/url"
+	"strings"
 
 	"github.com/BoltApp/sleet"
 	"github.com/BoltApp/sleet/common"
@@ -22,7 +23,7 @@ func NewWithHttpClient(username string, password string, merchantID string, URL
 		username:   username,
 		password:   password,
 		merchantID: merchantID,
-		URL:        URL,
+		URL:        normalizeURL(URL),
 	}
 }
 
@@ -38,6 +39,14 @@ func (client *CardConnectClient) buildURL(path string) (string, error) {
 	return url.String(), nil
 }
 
+func normalizeURL(URL string) string {
+	if strings.HasPrefix(URL, "http://") || strings.HasPrefix(URL, "https://") {
+		return URL
+	}
+
+	return "https://" + URL
+}
+
 func (client *CardConnectClient) sendRequest(request *Request, path string) (*Response, *http.Response, error) {
 	request.MerchantID = client.merchantID